The present invention relates to a map information regenerating device which is capable of regenerating map information stored in a map-information storage medium, such as for a vehicle travel guiding apparatus.
The Japanese laid open patent publication No. 4-50718 discloses such a vehicle travel guiding apparatus which is capable of displaying a current location of a vehicle on a road map shown on a display screen on the basis of area-map data read from a map-information storage medium by successively determining two-dimensional coordinates of the vehicle by cumulative calculation of detected distances and a direction of its travelling. This apparatus is characterized in that a current location of the vehicle, which is indicated as off a road on the road map as a result of an accumulated error, can be corrected in such a procedure that a pattern of the vehicle's travel trace to the present location and a pattern of a selected road extracted from the map data are compared with each other for a match and then the vehicle's position is aligned with the matched road.
The Japanese laid open patent publication No. 62-133600 discloses another travel guiding apparatus for a vehicle, which is capable of setting a start point and a target point on a road map shown on a display screen and searching digital map data to find an optimal (e.g., the shortest) course therebetween for the purpose of guiding the vehicle.
Map information to be used in the above-mentioned guiding apparatuses is generally stored as digitized data in a read only storage medium, e.g., CD-ROM. When the map is partially changed, for example, with the addition of a new road, the storage medium in use must be replaced with a new revised one. To cope with any change made in the road map, it has been proposed to use an additional read only memory (e.g., an IC card) for storing only revised map data, e.g., data relating to a new road or roads, in such a way that any changed information (e.g., a new road) may be read-out from the additional ROM and its image may be overlapped on a road map indicated on the screen, which corresponds to the basic (not revised) data read from the data base stored in the road map-information storage.
The drawbacks involved in the prior art devices are as follows:
First, every time a road map is even partially changed, which may frequently occur, it is required to replace a full storage medium with a new one. It is wasteful to use the storage medium in that way.
In the case when an additional ROM for storing changed data of the road map is used to read therefrom the necessary changed data of the road map and to display the changed portion image by overlapping it on a basic road map displayed on a screen, which is based upon the road map data read-out from the map information (data base) storage medium, it is only possible to add a new road but impossible to change and/or delete any road shown on the screen.
Particularly, overlaying an image of a newly laid-out road on the basic road map indicated on the screen may only synthesize two images without correlation between the changed data from a data correcting ROM and the basic road map data and, therefore, it cannot indicate whether a newly added road meets and crosses with an existing road or merely crosses over the latter without interconnection. In this case, it is also impossible to perform map-data processing such as pattern matching, optimal course searching and so on according to the revised map data.